Fix out-of-bounds in infcover tests.

Upstream zlib pull request: https://github.com/madler/zlib/pull/602

Bug: 225069280
Change-Id: I548a836096323053af225083916893b851532980
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3546708


Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/main@{#984579}
NOKEYCHECK=True
GitOrigin-RevId: afa134512eec0ab985c64bc39e39b0bb5212f8f6